1. Field of the Invention
The present invention relates to a data processing apparatus, a method and a program product for compensating for the photo proximity effect in order to sharpen rounded corners with a reduced amount of data, and a photomask fabricated using the same, for use in fabrication of semiconductor integrated circuit devices.
2. Description of the Related Art
In transferring the pattern of a semiconductor integrated circuit, exposure is performed by illuminating a photomask with light and thereby projecting the mask pattern onto a photoresist layer formed on a semiconductor wafer with reducing the size of the pattern.
In order to improve an integration degree and the operating speed of a circuit, a mask pattern has been miniaturized, and therefore, light passing through a photomask diffracts to cause the optical proximity effect on a wafer, thereby lowering a final transferred pattern resolution. For example, a rectangular feature 10 of a mask pattern as shown in FIG. 8(A) is transferred from the photomask to a photoresist on the wafer, and the final transferred pattern feature is round as shown in FIG. 8(B) due to underexposure at each convex corner.
In photomask fabrication, an electron beam or a short-wavelength laser beam has been employed for exposure in order to obtain a fine final pattern with high accuracy.
In a case where the electron beam is employed in photomask fabrication, as shown in FIG. 9(A), auxiliary features (serifs) 11 to 14 are synthesized for the respective corners of the original rectangular feature 10 in a photomask pattern in order to compensate for the proximity effect to obtain a final transferred rectangular feature as shown in FIG. 9(B).
In a case where the laser beam is employed in photomask fabrication, as shown in FIG. 10(A), auxiliary features (serifs) 21 to 24 are synthesized for the respective corners of the original rectangular feature 10 in a photomask pattern in order to compensate for the proximity effect to obtain a final transferred rectangular feature as shown in FIG. 9(B).
However, by adding auxiliary features to each original feature, the number of features increases by a great deal, which causes not only a data volume to become extremely large, but also an exposure time for scanning with a beam spot to become longer.
For example, in the case of FIG. 9(A), the number of figures in the corrected feature is 5 times that of the original feature 10. In the case of FIG. 10(A), since it is required to decompose each of the auxiliary features 21 to 24 into basic figures which can be processed in an exposure apparatus. As shown in FIG. 10(B), a triangle ABC of the serif 21a for example has to be decomposed into triangles ADO and OBO, each of which has a side being parallel with a side of the original feature 10. As a result, the number of figures in the corrected feature is 9 times that of the original feature 10.
Accordingly, it is an object of the present invention to provide a data processing apparatus, a method, a program product, and a photomask fabricated using the same, capable of not only suppressing an increase in the amount of corrected pattern data due to addition of auxiliary features but also effectively compensating for the optical proximity effect.
In one aspect of the present invention, a photomask has a corrected pattern having an original feature and first and second auxiliary features for the original feature. The first and second auxiliary features are added to both adjacent corners of the original feature. The both adjacent corners are located at both ends of a first side of the original feature. Each of the auxiliary features is a figure of a triangle or a tetragon, and the figure has one side which is an extension of the first side, and another side which is a portion of a second side of the original feature, the second side being adjacent to the first side.
With such a configuration, compensation for the proximity effect can be effectively performed. Further, in producing a corrected photomask pattern data, an enormous increase in the number of figures due to addition of auxiliary features can be suppressed.
Other aspects, objects, and the advantages of the present invention will become apparent from the following detailed description taken in connection with the accompanying drawings.